All I need is your power
by Kayalia
Summary: Sarah is powerful. She went through long trainings, journeys and met many creatures she shouldn't have. Catching the attention of people who find other uses for her than her magic, she doesn't have much time left. She must find it soon... Crossover with harry potter
1. Prologue

Prologue

There were things no one knew about Sarah Williams. She was no ordinary girl and if people knew all the things she had done, all the things that she lived through, experienced and learned, they would compare her to a goddess. Maybe she was in a part, for her family, her false family, never told her who her real parents were. And they never would since the Williams family died two years ago.

Sarah Williams Was seventeen when it happened. Upon solving the Labyrinth at the age of fourteen, she became a different person. She turned... Perfect. In every sense of the word. She had known she was different since turning six years old. Since she had found out of strange abilities she had. Talking with animals, this control over people, objects. She could make things move at will. She could fly. Fly, as in float around the room. With age her skills sharpened, and by luck, or something else, she found a small bookshop in Prattsville, a town just outside Montgomery, where she lived before moving to LA.

The shopkeeper seemed surprised to see her there, surprised that she even noticed the shop. For this wasn't a normal shop. It was the kind old shopkeeper, Sarah learned that he sold books about magic, very real magic. He sensed a strange power in this girl, and decided to tutor her. He would say that she had to be ready. He would never answer her what exactly was she supposed to be ready for.

She liked to learn. And she was good at it too. The shopkeeper, Wane, as he called himself, placed a spell that stopped the magical world from finding her. He was an outcast, and decided that he would take care of her so that she wasn't lost to the normal teachings of witchcraft. Wane spent ten years, teaching her everything. From Ancient runes, charms, transfiguration, animagi to logical reasoning, mathematics and sciences. He correlated the muggle world with the magical one, waiting for Sarah to understand how important both were. He then began teaching her other were darker spells, potions. Stronger and more powerful. He taught her a special language spoken by the old people of the North that created more options for her spell work. Sarah began to experiment. She had a talent for making new spells, new potions. She was a genius. A genius to the point of madness.

Wane made her a wand, a different wand. It was made out of diamonds, the outer layer made from dark wood, he would not say which tree it came from. The diamonds didn't come from our world, but from the Underground, a land dangerous and accessible to everyone but Wane. Those diamonds were stronger than anything else. Indestructible. And the core was the most surprising of all. It was Sarah's hair combined with one more. With the hair of the most powerful creature in the wouldn't say taught her wandless and non-verbal.

She studied ten years, hard, without a break, to become so powerful. She even began fighting she was fourteen she wished away her brother. She met one of the legendary creatures, a Fae, the Goblin King, who seemed to show too much interest in her. He tried to sway her with gifts, romance, all unsuccessful. She had bested by that she had made an taught her many things. To calm down in difficult situations. To be loyal towards her family. To respect other creatures and also made her stronger magically. She became too powerful for Wane. But there were so many things she still had to she couldn't do on your own. Because, the nature of Sarah's problem was her indecision. She didn't know on which side she was on, good or bad. And that would take a bad turn for her.

Then Wane disappeared.

He disappeared one year after Sarah's family tragic death in the fire.

The next year she was gone too.

**AN: this Sarah is not ideal. She will have many weaknesses revealed in the next chapter if you want me to continue that is. I hope that little thing you just read was to your liking and since its the first chapter, I would like to know what you think about it.**  
**Kayalia**


	2. Everyone needs an Achilles heel

Chapter 1

How rude

" Name?"

" Sarah Williams"

" Age?"

" Seventeen"

" Date of birth?"

" December 13th, 1928"

" The purpose of your arrival?"

" I would like to join the seventh year at your Institute"

" Family?"

" Deceased"

The cold voice continued to ask questions in the most unsympathetic voice he could master. He, being the principle of the institute. Professor Dippet. The headmaster of Hogwarts. " Show me your grades please" he commanded coldly, while sitting in the tall chair behind his massive table. Sarah who was sitting opposite to the cold man, glanced at the young Albus Dumbledore, who was leaning lightly against the wall, his twinkling eyes smiling at her with gentleness she didn't see since Wane's disappearance.

She bent to her bag and took out her reports. She passed them quickly over to the headmaster, her face remaining impassive all the while. While Professor Dippet looked through the papers, his eyes widening slightly.

" Those are perfect grades you have there miss Williams. Twelve subjects, twelve O's. I am impressed. I dare say you will rival one of our students quite well" he offered her a small smile. First one since Sarah entered the room.

" Thank you Sir" she answered politely.

" You will join our seventh year, and I suppose we shall sort you now, since we are all ready. Albus could you please get the sorting hat?" the man in question nodded, before walking over to the cabinet in the other chamber.

Sarah, who was sitting stiffly, her back straight and eyes calculating, began to look around the room, her eyes stopping briefly on the moving portraits, before moving to the ornamented cabinets. Dumbledore returned holding in his hand an old hat. It was made from an aged and tattered material, but it certainly did hold some spirit, moving on its own. Before she knew it, the hat was on her head, and a voice boomed in her head.

" _Good morning miss Williams! First time in Hogwarts eh? You are a bit off by a few years little time traveller. Now, where should I put you? There is something different about you, you have this powerful aura around you, this strength and wisdom. Experience that came from one particular journey too... Which house do you belong to, hmm miss Williams? It is not Hufflepuff, that for sure. Not rave claw either though you would fit there very nicely. So, Gryffindor or Slytherin? You belong in both, but as it is it shall be... SLYTHERIN!_" Sarah felt the weight of the hat being lifted from her head as she stood up.

" Thank you Professor" she said without any emotion.

Professor Dippet nodded in her direction.

" Albus could you please show Miss Williams around?"

" Of course Armando" the red haired wizard replied with a smile and walked up to Sarah. " Ready Miss Williams?" Sarah nodded.

" Good. let's go"

-/-/-/-/-/-/-/-/-/-/-

" Sir? I have heard of the library that Hogwarts is so famous for. I was wondering whether you could show it to me?" Sarah asked as she walked along Albus Dumbledore through the nearly empty corridor. It was almost dinner time, and most students were preparing for it, or stayed in their dormitories. Those who were out, gawked at Sarah, whispering excitedly, while pointing at her Slytherin badge on her chest. Dumbledore already showed Sarah the Slytherin common room, where Sarah left her belongings, after placing a heavy security charm upon them.

" Why of course. I am very happy that you ask miss Williams. We still have some time before dinner. Are you hungry?" Sarah looked up at the older wizard and smiled. She learned to like this man, who seeped with goodness.

" I am starving. But library is a place I have to see. I have dreamed of coming to see it since I have heard about it for the first time"

Dumbledore nodded.

" Yes it is a magical place on its own. You didn't tell Armando why exactly you didn't come earlier to Hogwarts" his twinkling eyes observed her calm demeanor.

" It was my mentor. He found me, or rather, I found him and his bookshop, and he decided he would tutor me. I have been living with muggle family, but it is to my knowledge that I have been adopted" she smiled fondly at the old memories creeping in. " And who were your real parents, if I may ask?"

Sarah shrugged.

" I don't know. My family died before they could tell me" she said, while her face revealed pain that was not there for a long while now.

" My condolences" Dumbledore managed to say, observing the girl next to him quite intently at this point.

" I keep them alive in my mind. They were the most... _good_ people I have ever met. They will always be there for me" _apart from my foster mother_ she thought sourly.

" This is one of those wisdoms that some never learn in the entirety of their lives" professor Dumbledore started " and I am proud to meet one so young who understands it".

Sarah didn't reply as the pair reached the doors leading to the library. Dumbledore stopped, letting her pass first.

" This" he pointed around him as they both passed into the room " Is the pride of our school. Centuries and centuries of collecting books, upholding traditions, and so on"

Sarah smiled as she detached herself from Dumbledore's company and walked up to the nearest bookshelves. She stopped before the old tomes and touched delicately the sensitive covers.

" I'll let you wander for a bit now. I will come for you in half an hour when the dinner starts" Dumbledore told her and she sent him a great smile in return.

" Thank you so much!" The professor gave her a smile of his own and left the room. Sarah turned back to see rows and rows of bookshelves and her heart leapt at the sight. Such a beautiful sight it was, one that filled her with peace. From the moment she was transported into this place, this time, 1945, she was scared, terrified. This was the place of knowledge, the one thing that would always calm her down. Knowledge equaled the way out of this terrible situation. It took her three days to find Hogwarts. Three days to find a good backstory. Three days to understand that she wasn't in her times anymore. And three days to start questioning her situation. There was no reason for her being here. And there was only one person who for certain could have a motif for bringing her here. The Goblin King. But why? Why would he want her to be he-

" Hello"

The sudden voice brought her out of her reverie. She looked up to see a tall, young man with peculiar grey eyes. Eyes were the first thing she saw, they seemed to change from grey to blue to green and back again, subtly of course. The boy was quite handsome with sharp cheekbones and black hair elegantly held back. He sent her a smile as he looked down at her new badge.

" A Slytherin! You must be the exchange student everyone seems to be talking about" Sarah raised an eyebrow at him. She has been in the castle for six hours and already she was the talk of the school. True, she left her things in the Slytherin rooms, but it still was fast nonetheless.

" Hello. I suppose I am" she offered a polite smile.

" My name is Tom Riddle. I am the head boy of the school"

Sarah nodded.

" Pleasure to meet you" she stated offhandedly, as her eyes drifted towards the books once more. Tom felt irritation swell inside him.

" And what's your name?" he asked, his voice cool and collected.

" Sarah... I am sorry I would like to look around the library. I have half an hour to dinner and I wanted to see this place for such a long time" she turned when Tom responded.

" I can show you around. I know this place better than anyone"

Sarah shook her head.

" I am sorry but I would like to be alone. Thanks" she added in an afterthought and walked away.

-/-/-/-/-/-/-/-/-/-/-

Tom wasn't sure why this stranger didn't fall to his charm. By all rights she should have! He could feel the power oozing out of her body in heavy waves, she didn't hide her powers. He liked that. What he didn't like was that she completely ignored him! Tom looked calmly at the girl who walked around, her face filled with wonder at the sight of books. He liked that very much. She wasn't some thick headed girl like all the others. He could have a use of her. He frowned. The problem was her. She didn't seem to want to cooperate. Well, she was a Slytherin, he had all the time in the world. Tom Riddle was curious for the first time in a long while. While it was only Early October, he felt like ages have passed since his return to Hogwarts. And why didn't she come in September? He looked at the clock on the wall and stood up. It was time for dinner. He wanted to go over to the new girl and take her to the Great hall, when this old coot entered the library again and walked over to the girl. Well, he would just have to save her a seat then.

-/-/-/-/-/-/-/-/-/-/-/-/-

In the end she didn't sit with Tom. She sat at the very end of the Slytherin table, not too near, and not too far from him. She looked at him only once, nodding in acknowledgement, before taking out a book she borrowed from the library and focusing all her attention on it. The Slytherins sitting nearest to her looked quite scandalized, while the Gryffindors seeing this behavior started to murmur among themselves. Tom narrowed his eyes on one boy specifically. Charlus Potter, who eyed her with especial interest. Where was the Gryffindor/Slytherin rivalry when he needed it? He would have to do something about him. It was then that Professor Dippet decided for the final speech of the night. He stood up and Began.

" Dear all. I am quite sure that now that you are full, you wish nothing more than forest in your dormitories. Before you do, I would like to introduce our new student, miss Sarah Williams, who has come to study the final year at our fine school. Please be helpful when you can, and always offer help. miss Williams suffered from extreme losses and you are all to show her respect. That will be all for the notifications for tonight. Good night" and with that he sat back down. Sarah, who was reading her book up until the point she heard her name was looking around her blankly, still dazed with the informations she had just learned. Tom stood up and came towards her, however before he could get to her, another boy also seventh year stemmed to be quicker.

" Hello" the boy said to Sarah and gave her a warm smile " would you like me to show you the way? My name is Alphard by the way. Alphard Black" the girl looked up at him, and the boy gasped at the sight of her eyes. They were green with those peculiar golden streaks in them. He didn't see such eyes ever before but they dazzled him.

" Sarah" she reached out to shake his hand. He looked at her hand uncertainly, wishing to kiss it instead. In the end he settled for a firm handshake " Nice meeting you. Actually that would be very helpful" He grinned and waited for her to close her book after she marked her current place with a handkerchief and stand up. They left together, a warm atmosphere enveloping them.

" Its a pleasure to see a new student in our year. You know, every year we see the same people, and it is refreshing to see someone new" Alphard smiled at her as he watched her glide through the corridor. " It is a new experience for me too. I have been home schooled my whole life and didn't have much contact with other children" not a full lie. I did go to school, just not magical one.

" It certainly has its perks. Especially since you are a Slytherin" they laughed together, when suddenly another male voice called Alphard's name. The boy stopped and turned around to see a group of Gryffindors making their way towards them.

" Hi! Sarah, this here is the heartbreaker of Hogwarts, Charlus Potter. He is my good friend, though I have a strong suspicion that he didn't come here for me" Alphard laughed.

Charlus grinned and performed a mock bow, all the while looking at Sarah.

" Why of course. I was very curious as to our newest addition to Hogwarts. That you are so beautiful is just a nice addition" Sarah laughed.

" It is very nice to meet you Charlus. I don't want to say anything against my house but" here she lowered her voice conspirationately " the Slytherins are so stiff. Especially the Riddle guy. No offense to you Alphard. You seem to be an exception" she grinned at the boy.

"Yeah Alfie is different. He usually sits with us by the Gryffindor table because the rest of his house hates him. You should join too!" a ginger haired girl with freckles spilled over her face spoke.

" Sarah, this is the one and only, Molly Ann Weasley. With her temper she could freeze the bloody dragons" another boy, also ginger haired explained with a smile.

" And _this_ is my brother-" Molly started.

" George Weasley. The one and only" he sent Sarah a charming grin.

" It is such a pleasure to meet you! I wish I were in Gryffindor. The hat actually considered me for all the houses, and seemed to have a trouble picking out between Gryffindor and Slytherin..." Sarah stopped when everyone's faces paled.

" Good evening. I have seen Mr Black lead you to our dormitory, but I see he took a wrong turn. I thought I could be of assistance instead" the voice of Tom Riddle boomed from behind, as Sarah swirled to see the man himself standing relaxed, with a smirk on his face. A sudden irritation crept over her, as Sarah replied:

" Thank you, but he is doing a splendid job as it is. I have just met many fascinating people and I would like to talk more before we retire. But thank you for the thought Mr. Riddle" Sarah's voice turned icy cold and sharp as a needle. She felt a dislike towards the boy the first time she met him. She disliked the aura of arrogance that he wore around him, and it irked her.

" As you wish" he replied stiffly" if you do need help I will always offer it"

" thank you Mr. Riddle. I shall" Tom nodded towards her and with a quick turn left.

" What a pig" Molly Ann snarled.

" Molly!" George admonished her with mock horror " You have lost our bet!"

A wicked grin appeared on his face, while Molly's turned into a deep scowl. Sarah turned to Charlus who once again had a grin on his face.

" What's going on? What bet?" she asked warily, not sure whether she wanted to know.

" Nothing serious this time. Molly and George betted who will curse or insult Riddle first. They took the bet on the second day, after Riddle burned their clothes" Sarah tilted her head.

" Why would he burn their clothes?"

" They tried to burn his. He recompensed" his voice suddenly held a tinge of anger.

" It doesn't seem that bad. He didn't do anything wrong... Did he?" Alphard started to laugh.

" He sent a frog rain over our lovely friends for a week. Or rather, his henchmen did. But everyone knew that it was his invention of the spell. The teachers couldn't take it off for a week" everyone, save the two siblings laughed.

" Not funny" Molly murmured.

" Come on Sarah we have to get down to our dungeons" Alphard called out dramatically. Sarah giggled while Molly Ann narrowed her eyes with a smirk.

" That's what happens when you are a little sneaky-"

" don't you dare finish this Molly Ann" George stopped her " Only I can mock Alfie"

" Says who?" she demanded dramatically.

" Says I" here brother replied puffing his chest.

" Equivalent to none at all, I would say"

" Give up George you can't win with a woman. Especially not this one" Alphard laughed.

" I can die trying!"

" You are digging your own rave not me mate"

Those Gryffindors were so dramatic, Sarah mused with a smile.

She didn't feel anything on her left heel. If she did, she would be terrified at a symbol that slowly spread to fill her whole foot. And if she listened very carefully she owuld be able to hear an ancient voice chuckling triumphantly.

**AN: hello there, just a quick note. I wanted to say that the chapters will most probably get longer. Secondly Sarah's presence at Hogwarts will switch on and off with another place we know, and there will be many twists and turns on the way. I hope you liked it, and if you did please review. **

**Kayalia**


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